NAOJ GW Elog Logbook 3.2
We star by checked the double-pendulum system which were moved form warehouse to TAMA central room.
We found that coil mass and electric cable were missing (fig 1-2).
We opened PD vacuum chamber and we found a completely assembled isolator stack with a double-pendulum system (fig 3).
(It was meant to be used to suspend a signal recycling mirror in TAMA.)
We checked this system too and we found that just the electric connectig cable was missing.
Since this vibration isolation system (both double pendulum and stack isolator) is in a better condition than the one stored in the warehouse,
we planned to use this one for suspending filter cavity input mirror in NM2 vacuum tank.
In order to do that, we checked that system dimensions were compatible with the ones needed for NM2 tank (fig 4-5).
Next week we will remove current TAMA SAS system from NM2 vacuum tank and we will replace it with the vibration isolation system at present placed in PD vacuum chamber.
On 11 November, we finished the following works.
1) fixing the TAMA SAS system,
2) unscrewing TAMA SAS system from the bottom of the vacuum tank. and
3) we found a hanging frame for TAMA SAS system at TAMA west-end room.
Ishizaki-san will move it to TAMA center room.
4) a double-pendulum system and bottom plate of the stack isolator
were moved from warehouse to TAMA center room.
Now TAMA SAS system is ready to remove.
Workers: Eleonora, Tatsumi
[ WORKERS ] Tatsumi and Takahashi
We opened the tank and then check TAMA SAS system
to remove from the tank.
You can find the procedure to air explosure of NM2 tank
bellow.
I did again measurements on the surfaces of some new SiC samples.
The number of samples this time was 6 from two companies: 3 samples from "NihonFineCeramics" and 3 samples from "Coorstek".
The average surace height distribution (Sa) has been found with Zygos NewView instrument to be 10 ~ 12 nm, for all samples. The measured window has been chosen to be 3x3 mm (2.5x mag.). Thus, the resolution is not particular high. Therefore, and also as we found some irregularities in the measured Sa values at higher resolutions (50x mag.), we made an additional measurement with the AFM in ATC on a randomly chosen spot of the third sample from "Croostek". The determined value of Sa with the AFM is 16.2 nm.
Attached to this report are the taken pictures of the height profiles. The first three are from "Croostek", the other three from "NihonFineCeramics". In black/white, the AFM picture is shown.
I used the Fresnel laws to determine wether or not the angle 12° would affect the Reflection measurement.
If the light was polarized the difference between 12° and 0° would be 2.5%
But the spectrophotometer SolidSpec-3700 have unpolarized light, and the difference between 12° and 0° is a factor of 1.5e-5 (0.0015%).
Not enough to affect the measurement, unless the light was polarized for some reason.
Members: Tatsumi-san, Manuel
Before making the glueing work it is necessary to pour First Contact polymer on the central area of mirror surface. We tried to do that but we had some troubles. I attach the pictures to show the problem. If the flow from the bottle is not continuous, the liquid splatters around and so we got some droplets in the area which is not to be covered by FirstContact. So we had to add FirstContact on the droplets and peel it up to clean them. The droplets went also on the edge and we had to apply the FirstContact with a brush. and using a smaller bottle.
I plot the same thing in a wider range, up to 5cm or radius to see how the graph goes to zero.
In the second figure I take the second derivative of the optical path with respect to the radius. The second derivative should de proportional to the focusing power, hence, to the signal of the absorption system.
It is the same for the bulk and for the surface absorption
I measured 3 samples of GaAs wafer from LMA.
Reflection measurement is taken at 12°.
Light is not polarized.
Plots show the spectrum of Transmission, Reflection and Absorption ( A = 100% - T - R ).
At 1064nm the absorption is about 4%. After 1300nm absorption becomes negative, down to -2%.
I used the Fresnel laws to determine wether or not the angle 12° would affect the Reflection measurement.
If the light was polarized the difference between 12° and 0° would be 2.5%
But the spectrophotometer SolidSpec-3700 have unpolarized light, and the difference between 12° and 0° is a factor of 1.5e-5 (0.0015%).
Not enough to affect the measurement, unless the light was polarized for some reason.
I made cross-checkings for Shoda-san's measuremets of "SPARE MIRROR" at Kagra site.
1) OSEM flag position on mirror
Within the accuracy of 1mm, these measurements are almost consistent with the design.
Only a measured value of the upper edge of the mirror was wrong.
2) Relative position of OSEM flag respect to the through-hole
After the hanging, it seems that the mirror is placed on 6mm upside from the mirror box.
I confirm it by making a drawing as attached.
The Remaining 37 OSEMs are now being cured in the ISO-1 clean booth in the ATC multipurpose experimental room!
Don't touch them for a couple of days.
Previously I did this 30 OSEM coils, and today 37coils, that means there will be 67 OSEMs in total. The number is sufficient for iKAGRA, but not for bKAGRA, as at least 70 OSEMs will be required for the bKAGRA (PRM, PR2, PR3, BS, SRM, SR2, SR3).
There are some OSEM coils washed or unwashed and used for trials of several process for the assembly, and they should be added to the number to fulfill the required numbers.
I draw on Inventor the mirror mount for the tama-sized mirrors (d100 x 60).
The picture shows the transation stage part where the mount have to be fixed.
I attach a pdf of the drawing (actually, the top view shouldn't be red, it's a problem of the conversion to pdf, so I also attach the bitmap of the topview).
The yellow part is peek plastic, which is in contact with the mirror.
The red part is the part that have to be fixed permanently to the translation stage.
I put a precision pin, to attach the mirror mount always in the same position.
I finished the (final?) simulations regarding the scattering of the BS recoil mass with the revised model of the BS, which I got from Fabian.
Basically, as expected, no significant effect could be found on KAGRAs sensitivity.
However, I have widen the previous model with the view on the clear-aperture of 195mm. Additionally, I found a way how to add a quasi-elliptical light-source for the mirrors surface, which is of great advantage for increasing the resolution of the results and to minimize the statistical error.
Right now, the error for the maximum values is ca. 10% but further decreasing it is no problem because of the mentioned reasons. Maybe, I will make another simulation run on Monday with increased resolution, also because of having better results for my paper.
2nd IM was almost assembled and shipped to Kamioka together with the 1st IM.
In the 2nd IM, one of the screw was stucked when assembling the side wall (spring side).
I think shorter screw can be inserted, but the long screw cannot be screwed fully now.
Anyway, it works without that screw.
And the heat shrink tube is running out.
So I did not connected the top picomotor cable.
Plus 5 OSEM coil bodies are washed (by ethanol), and then 67+5 = 72 OSEM coil bodies will be available in the end.
A short notice: I confirmed the LOCTITE vac seal can survive with ethanol in the ultrasonic bath.
I took some picture while the workers were repairing and repainting the floor during these three days.
Their work was basically
- Scratch the old floor and clean to the concrete.
- Paint the concrete with a black paint.
- Put a layer of green paint
- Put a second layer of green paint.
Ikenoue, Fabian, Fujii, Shoda,
Ikenoue-san told us how to use the winch system.
We tested the winching with 0.2mm piano wire and 0.65mm Tungsten wire.
We successfully lifted 4 kg and 7.2 kg weights by both wires.
The new winch system is fine for thick wires such as 0.65mm Tungsten wires.
We should add is some marks to indicate the way to turn the nobs.
And when you put the winch system on the IM, please remove the cable clamp and put the cable inside the IM, otherwise the cable will be sandwitched.
37 OSEM coil bodies are now packed into clean bags. (Akutsu, Fujii)
I tested how He would influence the time of the cooling-down and the warming-up of the cryostat.
For testing the cooling-down, I injected 20Pa of He gas in the tank and started the cryo-pumps. Interestingly, by reaching 250K, the temperature curve started to decrease less than the curve for pure vacuum. It then approaches to a temperature of ca. 180K. By pumping off the He inside the tank, the curve decreases as usual again (first picture, red curve). It seems that the isolation around the cold finger is not very good and He started to become a heat-bridge...
Warming-up the cryostat, on the other side, becomes now a very fast thing by injecting He gas: after 50h, I reached room temperature again. This is very convenient compared to the one week (!) we needed with pure vacuum.
The temperature curve for warming-up the cryostat can be seen in the second attached picture.
(Because of the low-temperatures, when I injected some He into the tank, I could not control the final pressure properly. That is why I got 62Pa in the end and not 20Pa as I was aimed for...)
